Washington: Researchers have found a way to calm fears with a drug that alters brain chemistry and help in understanding people at risk of anxiety disorders, including those suffering post-traumatic stress disorder (PTSD).

"What is most compelling is our ability to translate first from mice to human neurobiology and then all the way out to human behaviour," said Ahmad Hariri, neurobiologist at the Duke Institute for Genome Sciences & Policy. "That kind of translation is going to define the future of psychiatry and neuroscience."

The common thread in their studies is a gene encoding an enzyme called fatty acid amide hydrolase, or FAAH. The enzyme breaks down a natural endocannabinoid chemical in the brain that acts in essentially the same way that Cannabis, a.k.a. marijuana, does (hence the name endocannabinoid), reported the journal Molecular Chemistry.

Earlier studies had suggested that blocking the FAAH enzyme could decrease fear and anxiety by increasing endocannabinoids. (That's consistent with the decreased anxiety some experience after smoking marijuana), according to a university statement.

In 2009, Hariri's lab found that a common variant in the human FAAH gene leads to decreased enzyme function with affects on the brain's circuitry for processing fear and anxiety.

In the new study, Andrew Holmes' group at the National Institute on Alcoholism and Alcohol Abuse tested the effects of a drug that blocks FAAH activity in fear-prone mice that had also been trained to be fearful through experiences in which they were delivered foot shocks.

Tests for the ability of those mice to get over their bad experiences found that the drug allowed a faster recovery from fear thanks to higher brain endocannabinoid levels. More specifically, researchers showed that those drug effects traced to the amygdala, a small area of the brain that serves as a critical hub for fear processing and learning.